The importance of conceiving human development as a complex system
Authors: Sebastián Javier Lipina
Journal: The Lancet Global Health (2022)

The findings of the work of Aryeh Stein and colleagues in The Lancet Global Health1Stein AD Adair LS Donati G et al.Early-life stature, preschool cognitive development, schooling attainment, and cognitive functioning in adulthood: a prospective study in four birth cohorts.Lancet Glob Health. 2023; 11: e95-104Summary Full Text Full Text PDF PubMed Scopus (3) Google Scholar extend those of several generations of studies that have reported associations between early growth and cognitive development during different stages of the life cycle. In a study of 2614 individuals, Stein and colleagues not only found that early-life stature and childhood IQ were positively correlated, but also that adult IQ and schooling were better explained by early IQ than by early stature. In other words, these results suggest that both early cognitive development and schooling are independently important for adult IQ, and that early height would not contribute substantially to the variance of adult IQ beyond its association with these factors at early stages. These findings suggest not only the importance of early interventions for cognitive development, but also the need to unravel the multiple factors that influence developmental dynamics. The implications of this study are several, both at the epistemological level and in terms of the design and implementation of policies. First, the findings help to rethink the associations between growth and cognitive development, an area in which innovation and avoidance of reductionism are always necessary. Second, this study uses information from four cohort studies from different low-income and middle-income countries, which not only strengthens the value of the findings, but also helps to support scientific innovation and policy design. Epistemologically, unravelling the dynamics between different factors (ie, individual and contextual) contribute to contemporary systemic-relational conceptions of human development. This implies considering that the development of an individual is a complex system that involves different levels of organisation and interdependent subsystems. Consequently, the evolutionaly dynamics of the developmental trajectories are not necessarily linear or uniform, and adaptation to possible environmental disturbances involves adaptive changes that can give rise to both vulnerability and resilience phenomena.2García R Sistemas complejos. Conceptos, método y fundamentación epistemológica de la investigación interdisciplinaria. Gedisa, Barcelona2006Google Scholar, 3Lerner RM Concepts and theories of human development.4th edn. Routledge, New York, NY2018Crossref Scopus (23) Google Scholar Following such logic, Stein and colleagues interpret their results as evidence that aligns with the objectives of the nurturing care framework. This proposal could be conceived as systemic-relational to the extent that (A) it assumes the importance of nurturing care and protection as a systemic effort that involves different sectors, and (B) it implies the need to implement various interventions from the prenatal stage and during at least the first decade of life, aimed at satisfying different needs originating from multiple types of exposure to developmental risks and adversities.4Britto PR Lye SJ Proulx K et al.Nurturing care: promoting early childhood development.Lancet. 2017; 389: 91-102Summary Full Text Full Text PDF PubMed Scopus (775) Google Scholar One of the most important challenges that these conceptions of development impose on the design and implementation of care and protection policies is the existence of different human populations exposed to different risks, adversities, and opportunities, the combinations of which generate variable trajectories of different attributes of development. This implies that the design and implementation of interventions require adjusting to different risks and developmental trajectories, instead of conceiving homogeneous interventions for the same population group or exposure to a unique type of risk (eg, low income). Another challenge is to continue exploring different ways to operationalise complex constructs such as growth, schooling, and cognitive development. Each factor involves phenomena that can be operationalised in varying ways depending on different theoretical frameworks, methodological paradigms, and even logistical and implementation possibilities and obstacles.5Goyal MS Iannotti LL Raichle ME Brain nutrition: a life span approach.Annu Rev Nutr. 2018; 38: 381-399Crossref PubMed Scopus (28) Google Scholar In this context of challenges, some innovative projections that could continue the effort made by Stein and colleagues could be to (A) identify within each cohort subgroups of children exposed to different constellations of risks, adversities, and opportunities;6Caspi A Houts RM Belsky DW et al.Childhood forecasting of a small segment of the population with large economic burden.Nat Hum Behav. 2017; 1: 0005Crossref Scopus (186) Google Scholar (B) explore the possibility of differentiating operationalisation of the schooling construct as an intervening proxy based on each sociocultural context; and (C) update the analyses implemented to explore hypotheses of specific associative dynamics for each subgroup of constellations of risks, adversities, and opportunities on the basis of more comprehensive systemic-relational conceptions of development. Future studies should integrate cognitive and emotional differentiated processes to begin to operationalise self-regulation phenomena that can be measured with complementary instruments to standardised intelligence tests. This method would make it possible to further deepen knowledge about the opportunities and difficulties of development of different subpopulations of children. Finally, these efforts will continue to require the setting-up and training of interdisciplinary and intersectoral teams, with the inclusion of people from communities. One of the main aims of these types of teams should be the innovation in the co-designing of scientific studies and decision-making algorithms that in turn guide the design and implementation of interventions with societal values7Novitzky P Bernstein MJ Blok V et al.Improve alignment of research policy and societal values.Science. 2020; 369: 39-41Crossref PubMed Scopus (44) Google Scholar that are as specific as possible for subgroups of children with different constellations of risk and adversity. This set of efforts might result in a more heterogeneous conception of human development, which contributes to making visible the diversity of trajectories of different attributes or the same type of attributes conceptualised and operationalised in the context of the diversity of experiences, vulnerabilities, and possibilities of resilience in different regions of the world. I declare no competing interests. Early-life stature, preschool cognitive development, schooling attainment, and cognitive functioning in adulthood: a prospective study in four birth cohortsThe observed associations of early-life stature with adult IQ and schooling varied across cohorts and sexes and explained little variance in adult IQ beyond that explained by child IQ. These findings suggest that interventions targeted at growth for health and early development are important. Our results are consistent with the inference that improving long-term cognitive outcomes might require interventions that more specifically target early cognitive ability. Full-Text PDF Open Access